1. Field of the Invention
The present invention relates to an electrostatic charge latent image member for use in such as an electrophotographic machine capable of simultaneously performing such process as charge not by the corona discharge, exposure, developing, cleaning and the like.
2. Description of Related Art
As for an electrophotographic machine, the one that employing the corona discharge is generally well known. FIG. 1 is a schematic view showing an electrophotographic machine employing the corona discharge. In the figure, there are arranged around an electrostatic latent image member 30 a charger 31 for performing such process as corona charge, exposure, developing, transfer, cleaning, erasing, or the like, a developing unit 32, a transfer unit 33, a cleaner 35, an erasing lamp 34, and the like. The electrostatic latent image member 30 is to take the following process repeatedly while being rotated. The electrostatic latent image member 30 is electrified by the charger 31 so as to form an electrostatic latent image by projecting an optical image, and then the developing unit 32 forms a toner image and the transfer unit 33 transfer it on a recording paper 37 and a fixing unit 36 fixes it on the recording paper 37. At that time, the cleaner 35 removes residual toner and the erasing lamp 34 erases residual electrostatic charge. Accordingly, there has been a disadvantage that both constitution and process of the conventional machine is complicated.
In order to avoid this disadvantage, the electrophotographic machine not employing the corona discharge is proposed recently in such as J. Appl. Phys., Vol. 63, No. 11, Jun. 1, 1988. FIG. 2 is a schematic view showing an electrophotographic machine not employing corona discharge where there are arranged a magnetic brush 41 on the upper periphery of the electrostatic latent image member 40, a transfer roller 42 on the lower periphery of the electrostatic latent image member 40, and an LED array head 43 inside the electrostatic latent image member 40.
The electrostatic latent image member 40 is composed of layers, a transparent electrode 40b, and a photoconductive layer 40c comprised in a photosensitive unit on the outer periphery of a transparent supporting member 40a made of glass. Between the transparent electrode 40b and a magnetic roller 41a in the magnetic brush 41, applied developing bias. Low-resistance toner is to be stuck to around a sleeve 41b which covers the periphery of the magnetic roller 41a to form the so-called magnetic brush 41, the magnetic brush 41 being in contact with the periphery of the photoconductive layer 40c, generates a strong electric field between the surface of the magnetic brush 41 and the photoconductive layer 40c. In this state, the conductive toner layer rubs the photoconductive layer 40c to intensify their electric contact with each other so that electric charge is easily to be injected, and by the injected electric charge being trapped the photoconductive layer 40c is to be electrified. When the electrostatic latent image member 40 is electrified up to generally the same potential as that of the toner layer, electric attraction is not generated between the toner and the electrostatic latent image member 40, so that the toner is prevented from sticking to the surface of the photoconductive layer 40c. In this state, because when an optical image projected from a head 43 enters the photoconductive layer 40c from the inside of the transparent supporting member 40a, potential of its exposed portion is reduced, according to the principle of the inversion, the toner comes apart from the magnetic brush 41 and then sticks to the photoconductive layer 40c to form a toner image which is to be transferred on a recording paper 44 by a transfer roller 42.
Residual toner on the surface of the electrostatic latent image member 40 is removed by both scrubbing force of the magnetic brush 41 and magnetic force of the magnetic roller 41a. Accordingly, charge, exposure, developing, and cleaning of the electrostatic latent image member 40 are generally simultaneously performed by the magnetic brush 41 and the head 43, which results in such an advantage that constitution and process of this apparatus is greatly simplified.
However, in the photosensitive unit of this electrophotographic machine being different from that of the conventional one, mainly travels a carrier with polarity opposite to that of charge of the photosensitive unit, which results that it is difficult for this photosensitive unit to obtain clear images.
As has been aforementioned, for the above-mentioned electrophotographic machine, it is necessary that the injected electric charge by the toner layer should be trapped at the electrophotographic process.